Fuel supply control system for supplying multiple combustion zones in afterburners



June 20, 1961 M. J. coRBET-r 2,988,883

FUEL SUPPLY CONTROL SYSTEM FOR SUPPLYING MULTIPLE COMBUSTION ZONES IN AFTERBURNERS 2 Sheets-Sheet x Filed April 2, 1956 June 20, 1961 M J coRBET-r 2,988,883

FUEL SUPPLY CONTROL s'YsTEM PoR SUPPLYING MULTIPLE COMBUSTION ZONES IN AFTERBURNERS Filed April 2, 1956 2 sheets-sheet 2 .LLL/E lfm* Mama/f d am# y Z7, Z155 United States Patent() 2,988,883 FUEL SUPPLY CONTROL SYSTEM FOR SUPPLY- ING MULTIPLE COMBUSTION ZONES IN AFT- ERBURNERS Marshall J. Corbett, Mayfield Heights, Ohio, assigner to llxltilmpsonv Ramo Wooldridge Inc., a corporation of Filed Apr. 2, 1956, Ser. No. 575,624 7 Claims. (Cl. 60-39.28)

The present invention relates to improvements in mechanisms for controlling the ilow of fuel to a combustion zone and mo-re specifically to a valve control arrangement which will supply fuel to a multiple-stage afterburner and will vary the number of stages used and amount of fuel fed in accordance with the selected fuel to air ratio and in accordance with the amount of air passing through the combustion area,

In engines provided with combustion areas requiring the supply of fuel, such as turbo-jet engines having afterburners, it is sometimes necessary to use multiple com'- bustion zones in order to provide a Wide range ofy afterburner fuel-air ratio modulation. The demand for, this Wide range is caused by variances in desired fuel-air ratio and variances in the amount of air being forced through the combustion area. In the use of multiple combustion zones, it is desirable to be able to vary the number of zones and be able to accomplish this variance smoothly Without seriously Varying the fuel to air ratio when changing numbers of combustion zones and without affecting the operation of the afterburner. In making the transition wherein the number of combustion zones used are changed; the sensitivity of the control for selecting fuel-air ratio should ideally remain constant and the total amount of the; fuel fed tothe afterburner combustion area should be constant, or shouldk decrease or increase in a smoothcurve as the number of combustion areas are changed.

Fur-ther, for the maintenance of aconstant fuelV to air ratio with variances in the amount of air, thechange between the number of the combustion areas used should be automatically and easily accomplished. Also, the change in the number of combustion areasl used should be ableto be accomplished smoothly by manual change in the fuel to air ratio, or by automatic change in fuel'` to air ratio due to a condition-responsive control.

In supplying` fuel to an afterburner with a widevvariance in desired fuel supply, it should be possible Vto accomplish the variance with one fuel flow control: unit to achieve improved and more accurate control wit-h sim.- plicity of structure.

In accordance-with the foregoing, it is an object of the present invention to provide afuel flow control mechanism which is capable of accurately regulating the supply of fuel to the combustion areaV over very Wide ranges of fuel demand.

It is another object of the invention to provide a fuel supply controlV valve mechanism which will control variances in fuel demand by controllably varying the num.- ber of combustion zones utilized.

Another object ofthe present invention is to provide a fuely ow control mechanism which is capable; of supplying fuel to a plurality of combustion zones and changing the number of combustion zones while maintaining a uniform rate of change of fuel supply during theV change in the number of zones utilized.

Another object of the invention is to provide a fuel flowV control mechanism which is capable of varying the iiow of fuel in response to required changes infuel to air ratio where the requirements are obtained from a plurality of sources. i

ICC

A further object of the invention is to provide a fuel metering valve arrangement which Iwill vary the supply of fuel to a combustion zone in accordance with a combined control responsive to the amounts of air passing through the combustion zone and also responsive to a fuel to air ratio input signal.

Another object of the invention is to provide a fuel metering valve arrangement which will maintain a constant pressure differential across the metering valves regardless of amounts of fuel demand and regardless of the number of valves in use.

A still further object of the invention is to provide a fuel metering arrangement for supplying fuel to the combustion area of a multi-stage afterburner wherein the fuel supply is pressurized by an air turbine pump and the performance of the air turbine pump is not affected by the selection of different afterburner combustion Zones.

Other objects and advantages will become more apparent from the following specification and claims taken in connection with the appended drawing in which:

f FIGURE 1 is a schematic view of the structural arrangement of the mechanism embodying the preferred features of the invention; and,

FIGURES 2, 3 and 4 are enlarged detailed views of portions of the mechanism of FIGURE l, with FIGURE 3 being a sectional view taken substantially Valong line III- 111 of FIGURE 2.

In general, the operation of the mechanism illustrated in the drawing is to deliver metered fuel to a combustion area such as the afterburner of a turbo-jet engine. The combustion area is shown generally at 10- and -is comprised of a plurality of combustion zonesl each` of Iwhich is fed by a separate fuel distributor line, the separate fuel lines mentioned being shown at 12, 14l and 16. The lines may be connected at their discharge ends to ring mani-folds or the like, not shown, Which comprise the separate combustion` zones and which are separately operated and separately supplied with fuel through a common supply control which will be described.

The supply of fuel which is to -be metered to the afterburner area enters the control valve mechanism through a fuel line at 18 and the fuel is pressurized by an air turbine driven fuel pressure pump 20. The turbine pump which pressurizes the fuel supply is, controlled by an air turbine valve shown generally at Z2 in the lower righthand corner of the drawing. This control valve automatically controls the speed of the air turbine pump to thereby control the pressure of the fuel supplied to the con-trol valves. Y

The fuel is'metered to the combustion zones by metering or control Vvalves and the amount of fuel` fed by these automatically controlled valves is controlled by two primary factors. These factors both functionto maintain a selected fuel to air ratio. The first determining. factor is the amount of air passing through the engine and flowing into the afterburner chamber. It will be apparent that this is a critical factor to maintaining the given fuel to air ratio.

The second determining factor is the selected fuel to air ratio itself and this factor is fed` into the machine either manually such as by a hand control lever 27` or auto;

Vmatically as by a pressure ratio sensing dev ice 28. The

hand lever and pressure ratio sensing device both send a' control signal to determine the position ojf the fuel oW valve arrangement and the signals will modulate each other to obtain the proper fuel to air ratio inthe afterburner zone.

valve control signal to control the apparatus shown generally at 30 for controlling the position of the fuel ow metering valves.

Each of the three described control elements and the other units will be separately described in detail in accordance with their structural relationship and functional relationship with respect to the mechanism as a whole and each section of the specification will be titled in accordance with the portion being described.

Fuel pressurizing mechanisms The afterburner or combustion fuel is supplied through a pump inlet pipe 18 leading to the air turbine afterburner fuel pressure pump 20. The fuel enters the inlet of the pump and passes through the impeller 21 to leave the pump through the outlet pipe 24 in a pressurized condition.

After leaving the impeller vanes 21, the fuel passes through the diffuser section 23 of the pump and hence upwardly as shown in the drawing, to the outlet pipe 24 which leads to the manifold chamber 26 feeding to the inlets of the separate fuel ow control valves.

The fuel pump is driven by an air turbine 29 having blades shown at 29a mounted on the shaft 31 on which is also mounted the impeller 21 of the fuel pump. Pressurized air, which is supplied from the compressor of the main turbo-jet engine enters the fuel pump air turbine through the chamber 34 and the amount or pressure of the air entering this chamber is controlled by a gate valve 32. The gate valve is operated by the air turbine pump control valve 22 in a manner which will be later described in detail. In any event, the air which enters the air turbine controls the speed of the fuel pump and hence controls the pressure of the fuel which is discharged from the pump 20 into the line 24 and to the valves through the manifold 26.

The position of the gate valve 32 and speed of the air turbine pump is regulated by the control valve 22 in order that the fuel will have a constant pressure differential across the control valves and this pressure differential can be controlled by regulating the pressure of the fuel as it enters the valves in the manifold 26.

Fuel flow control valves Separate and individual valves are used to control the ow of fuel to the combustion area with the separate valves being shown at 36, 38 and 40. These valves are also labelled No. 1, No. 2 and No. 3 and for convenience will be thus referred to. The valves are each provided with a seat formed in the casting 42 common to all the valves and the valves are mounted for concurrent movement on a single valve stem 44. Each of the valves is arranged on its stem so that they will be moved an equal distance from their seat and since the valves are of equal size or area the flow through each of the valves will be the same. The ow through the valves is, of course, dependent on the valve area which is the same and also on the pressure drop across the valve, and as will be seen from the later description, this pressure drop is kept uniform for each of the valves. Connected between the outlet side of each of the valves and a combustion zone in the afterburner is a distributor line, the lines being shown at 12, 14 and 16. Each of these distributor fuel lines leads to a separate manifold or to a separate combustion zone in the combustion area of the afterburner. With the use of multiple combustion zones, the fuel-air ratio can be varied over a very considerable range.

As was previously mentioned, in order to obtain a predetermined ilow across the valve No. 1 for a given opening in the valve, the pressure drop across the valve and hence the fuel flow for a given opening is maintained constant by control of the pressure of the fuel as it is pumped to the valves. Each of the succeeding valves No. 2 and No. 3, has its own pressure regulator which meas- 4 Y ures the pressure head across the valve and reduces the discharge pressure if necessary to maintain a substantially uniform pressure in each of the three distributor lines. It will, of course, be seen that if a certain ratio of pressure as between each of the distributor lines is desired, this can be obtained by selecting pressure regulators for the separate valves each of which will obtain a different pressure in the distributor line.

Thus when all three of the valves are feeding fuel to the afterburner combustion area, the fuel passing through valve No. 1 leaves the manifold 26 entering through the valve inlet 44, the fuel for valve No. 2, leaves the manifold 26 entering through the valve inlet 46, and the fuel for valve No. 3 leaves the manifold 26 entering through the valve inlet 48. The pressure regulating valve for valve No. 2 is shown at 50 and the pressure regulating valve for valve No. 3 is shown at 52.

The regulating valve 50 for valve No. 2 has a piston 54 slidably contained within a cylinder 56. A fuel pressure line 58 leads from the inlet side 46 of valve No. 2 to the cylinder 56 on the back or high pressure side 57 of the piston 54. The cylinder on the low pressure side or the rod side 55 of the piston is vented through line 59 which connects through valve 94 to the drain line 60 which leads to the fuel inlet line 18. The fuel inlet line 18 and drain line 60 are at a reduced pressure and for purposes of discussion may be assumed to be somewhere near atmospheric pressure. The pressure differential between the high pressure end 57 of the cylinder 56 which is at a pressure greater than atmospheric pressure and the low pressure end 55 is offset by a coiled compression spring 62 within the cylinder. The position of the piston 54 controls the position of a pressure regulator valve 64 which moves toward or away from the seat 66 in the casting 42.

The pressure regulator valve 64 also acts as a shutolf valve and this operation will appear later. In order that the valve 64 will be affected by the pressure of the fuel on the low pressure side of the valve No. 2 as well as on the high pressure side, the low pressure fuel is bled into the low pressure side of the regulating valve control piston 54. Through the center of the valve 64 and the stem or piston rod 54a which supports the valve from the piston 54, is a bleeder line 66 bleeding fuel from the output side 68 of the fuel control valve No. 2. The low pressure end 55 of the cylinder communicates with the vent line 59 but this is normally sealed by valve 92. Thus, in operation as a pressure regulator valve, the piston is pressurized on one side by the high pressure fuel and on the other side by the low pressure of the fuel bleeding through the line 66. The high pressure side is counterbalanced by the spring 62 and the piston thus moves back and forth to control the pressure in the distributor line 14 leading from the pressure-regulating valve 64.

A similar arrangement for regulating the pressure drop to the discharge side 72 of the ow valve No. 3 is provided in the pressure-regulating valve 52. The pressure-regulator 52 carries a valve body 74 which moves against a seat 76a to regulate pressure drop of the fuel passing through the ow valve No. 3. The valve body is carried on the piston rod 76 carried by a piston 78 movable in a cylinder 80. The high pressure side of the piston is subjected to high pressure fuel through a line 82 and the low pressure side 84 of the piston is subjected to low pressure fuel which is bled through a `bleeder line 86 extending through the center of the valve 74 and the piston rod 76. A coiled compression spring 88 on the low pressure side counterbalances the pressure on the high pressure side of the piston and causes the piston to operate as a fluid pressure-regulator -to move the valve 74 toward and away from its seat 76. Thus, for a given opening of the fuel flow valve No. 3 the pressure in the distributor line 16 will remain constant being controlled by the pressure-regulator valve 52. As

uS istlieca'se witlithe pressurer'egulator va'1ve50', the'- valve 52" mayf also bef operated asa shut-olf valvefor the distributbrlline-16 ina mannerA whichwilllater be--described.

Y 'Ihe low pressure side 80- of thepistoni 78 communicat'es with-line: 9'0'1 which joins the drain line 6tlleading baclftb the fuel supply line 18'1 but1 thisnormally is sealed off 'by' the valve 94.- i

Each; of' theve'ntv lines 58 and 90,-V before joining the drain linel 60 pass through valves192 and' 94, respectively, the valve', members 92 a'nd 943 are shown in the form of cylindrical sliding valveseach having asliding body member` 96 andi 98 connected? to a common. stem 100. 'Ihe Stem 10'0-is' cored: with. a pressure' relief line'102which prevents; pressure` from building upf in the end` chamber 104 ofthe valve body'106. The valve stem 100 is connected tora master fulcrum control. rod 206 which functionsk tozdetermineV the setting and the degree of controlof the fuelflow control valvesiinamanner that will be later described.

Y The iluid pressure-regulator valves 50` and 52 are in.- dividually closable to stop the flow through the distributor lines 1'4 and16, respectively. To accomplish. this, the vent lines 90 or 59` are normally shut off but. the valves 96 and 98- are selectively openable with the axial movement of thel valve-carrying stemr 100. As the stem, is moved downwardly as shown in the drawing,` the vent line 90 is rst connected to. thev drain 60y tol relieve: pressurev from beneath the piston 78 of the regulator valve 52. This causes the piston 78 to` move to the left, as shown ons theVv drawing, and snaps the valve head 72 against the seat 76 to thereby close the valve; This immediately stops the ow of fuel through the distributor line 16 and; fuel now is supplied to the combustion area only' through the lines 12 and"14.y At this same time, the valve stem 44 carrying valves Nos. 1, 2 and 3' is moved to the left immediately opening the two remaining operative valves No. 1 and No.l 2 anY additional amount to increase the llow through lines 12 and 14 to compensate fon the loss. of fuel flow in line 16. Thus, when any of the combustion zones are cut out, there is immediately an increase of fuel feed to the remaining combustion zones to cause a smooth transition and an even llow of power as the number of combustion zones in use is changed;

Asl the combustion zone selector valve stem 100y is moved further downwardly, as shown in the drawing, the line 59 is next vented and connected to the drain line 60 thus closing the valve 64. By venting line 59, the pressure in the chamber 56 beneath the piston 54 is suddenly reduced and the piston movesl downwardly, as shownin the drawing, to move the valve 64 against its seat 70. immediately terminates the flow through the distributorline 14 and after this time only the distributor line; 12 will be feeding fuel to the afterburner combustion. zone. The closing of the pressure-regulator valve 64, which is on the discharge side of fuel flow control valve No. 2, is accompanied by a sudden shift to the left of the valve stem 44 to open valve No. 1 further and compensate for the reduction of ow in fuel to the combustion area by the stopping of the line 14. It will be recognizedthat although valves Nos. 1, 2 and 3 are all mounted on the same stern 44, the movement of the remaining valves is not important since their discharge sides have been cut olf by the closing of the pressure-regulating valves 50 and 52.

The mechanism for automatically moving the valve stemV 4'4 and opening the fuel ow control valves to compensate for cutting off the distributor lines` will be later described in detail.

As hasbeen previously described, the ilow control valves automatically open to. give a greater flow for the valves v'vhitihy remaineffective. The reverse is true when the controlivalves 50 and" 52 are again opened. For each opening` the control' valves will: immediately and autortaticallyl move V.toward amore closed position to keep theftot'all ilowor fuel! tontheft'otal combustion area. at a constant rate ofl'decrease or increase;

Mechanism for controlling fuel supply Vpressure At; 221, inthe drawing, is illustrated the air turbine pump control valve. This valve contains a pressuresensitifve mechanis-ni= whichy is connected betweenV the pressurized fuel supply'and? the distributor line 12'. The valve measures-the pressurel head1 diierentialA which is the equivalent of the'dro'p in pressure across thefval'veNo. 1l and maintains -this pressure dropV atl aconstant. This is accom? plished by the valve 22 varying the speedI oft the. air turbine-pump 20l to thereby vary thev Vfuel pressurey supply in the' pipe 24 and the valve manifold 26.

The speed' of the aif'r turbine pump 28' is controlled' by the pressure of' the in the air supply chamber 34; This pressurized lair iis-obtained from the compressor of the turbo-jet engine, and is supplied through a conduit 108 leading to fthepressure system. The pressure for operating the air turbine pump 29is controlled by a gate valve 32 carried on the endV of a gate valve control rod 1112'. The gate-Valve control rod |112 connects to a piston 114 slidably mounted within a cylinder 116. The position of the gate valve controlpiston 114 is controlled by the pressures in the chambers within they cylinder 116 onl each side of the piston 114.-

TheA pressure for operating the piston 114 is obtained from the main air pressure line 108 which furnishes air to rotate the air turbine. Air fromthe pressure line 108 is led along the valve control rodw1'12 which is loosely fitted'- within the casting 118 and down through an air line 120 in the casting 118. The line 11201 leads downto a pressure chamber 122 through which passes a valve rod 124 carrying valve heads 126 and 128 on eaohend`. At fthe ends of the pressure chamber -122 are the valve chambers and 142 in which the valve heads move. Air i's fed to each end of the piston 114 by piston control lines 132 and -134 which lead upwardly to each side of the piston from the pressure chamber 122. The valve stern 124 is shown in the drawing with the valve heads 126 and 128 in the neutral or stable position wherein no movement of the speed control piston 114 will result. In the stable position,the air leaks from the pressure chamber 122 past each valve 126 andf 128 at an equal rate and thus the pressures in the chambers 127 and 130-011 each side of the control piston 114 will be equal and no move,- ment of the piston will occur.

The piston control air lines 132 and 134 are vented around the heads 1126 and 1-28` of the valves throughy the valve chambers 140 and 142- to the atmosphere with the line 136 leading to atmosphere from the valve chamber 140 and the line 138V leading to atmosphere from the valve chamber 142. These lines to atmosphere permit a small amount of pressurized air to bleed around the valve heads. If the valve stem 124 moves to the left, for example, the valve head 126 will seat on the left-hand end of the valve chamber 140 and the valve head 128 will seat in the left end of the valve chamber 142. The valve 126 will thus shut oli the line 136 which leads to atmosphere and this will cause a build up of air pressure in the valve chamber 140 and also in the chamber 127 to the left of the piston 1-14. Simultaneously, the valve head 1'26 will seat on the left-hand side of the valve chamber 142 permitting the air from the right-hand side 130 of the piston 114 to bleed rapidly out through line 134 and be vented to atmosphere through line 138. This will cause a rapid movement of the piston 11-4 to the right, as shown in the drawing, thus increasing the opening of the gate valve 32 and admitting more air to the chamber 34 to speed up the operation of the air turbine pump 29. This, of course, will increase the fuel pressure in the manifold 26. The increase in fuel pressure, of course, will have been made in response to a decreasey in pressure differential across valve No. 1. This decrease in pressure differential, is caused. either, by a drop in4 pressure ingthe n7 distributor line 12, as might be caused by an increased opening of the valve No. 1, or a decrease in fuel pressure on the inlet side of the valve.

Stability of the piston 114 is obtained by feeding back turbine air inlet pressure through line 1'15 to chamber 117 acting on a small plunger 119 connected to piston 114.

The distributor line 12 connects to the lair turbine pump control valve 22 through a line 144 which leads to one side of a diaphragm -146. The fuel pressure supply is led to the air turbine pump control valve by a pressure diaphragm line 148 which leads to the other side of the diaphragm 146.

On the drawing it will be noted that if the pressure in the fuel manifold 26 drops too low or the pressure dierential across valve No. 1 is too low the diaphragm 146 will move to the left thus causing the valve control stem 124, which is rigidly connected to the diaphragm 146, to move to the left as has been previously explained thereby causing the piston 114 to move to the right opening the gate valve 32 and speeding up the air turbine pump. This will have the eeot of increasing the pressure in the fuel pressure supply line 24 correcting the situation which existed.

If the diaphragm i146 is moved to the right due to too large a pressure drop across the valve 1 the pressure in the pressure fuel supply line 24 must be dropped. The diaphragm 146 moving to the right will cause the valve heads 126 and 1l28 to seat at the right of their individual valve chambers 140 and 142 thereby venting the left side 128 of the piston and pressurizing the right side 130 causing the piston 114 to move to the left and close the gate valve 32. This slows down the air turbine pump and elices the pressure in the fuel pressure supply mani- Means are provided to manually regulate the speed of the air turbine pump or to terminate operation of the mechanism. The manual control is provided through a solenoid-type regulator shown at 162. The plunger core of the solenoid 164 is carried within coils provided with electricity through leads leading to a suitable manual control switch, not shown, Which may be set by the operator. The solenoid plunger carries at its ends valves 166 and 168 each of which operates in a valve chamber 170 and 172 respectively. The valve chambers each have vent passageways -174 and 176 with the passageway 174 venting directly to atmosphere and with the passageway 176 leading to the atmosphere vent passageway 138. The plunger 164 is carried in a pressure chamber 175 which 1s supplied with pressure through line 180 which connects to the pressure cham-ber 122. The pressure chamber 175 connects to the ends of the cylinder 116 in which the valve control piston slides, by lines 181 and 182 leading to lines 132 and 134.

The solenoid plunger 164 is normally maintained in the central neutral position so that the valve members 166 and y168 will not afect the piston 114 or upper valve members 126 and 128. When manual control is to be effected, however, the solenoid is moved either to the right or to the left causing the valve members i166 and 168 to either bleed air from one side of the piston and admit pressurized air to the other side or vice versa.

Thus it will be seen that the air turbine pump control valve 22 automatically controls the speed of the air turbine pump to maintain fuel pressure in the pressure fuel supply line 24 and in the manifold 26 so that a constant pressure drop will occur across the valve No. 1. The pressure dro across valves 2 and 3 is also maintained constant by eir individual pressure regulator valves 50 and 52. Thus a uniform pressure will be supplied to the combustion area in the afterburner by each of the distributor lines 12, 14 and 16 leading to the individual combustion zones.

1,2'and 3 is controlled by valve control piston 150 which ,.8 is secured to the head end of the valve 1 and is, of course; interconnected to valves 2 and 3 through the stem 44., The piston is pressure-responsive and slides in a cylinder 152. The cylinder 152 to the rightv of the piston 150 is subjected to the pressurized fuel supply, being open to the fuel supply manifold 26. The left side of thepiston 150 is subjected to reduced fuel pressure which is fed into the chamber 154 behind the piston through a reduced pressure port 156. The fuel in this port is of reduced pressure, being bled off from the port 156 through bleeder line 158. Line 158 if opened at the end 184 will reduce the pressure in the port 156 and thus reducing the pressure in the chamber 154 behind the piston causing the piston to move to the left to carry the control valves 1, 2 and 3 to the left thus opening them. A needle valve 160 may be conveniently supplied to control the amount of fuel feed into the port 156. The pressure behind the valve control piston 150 is thus controlled by the amount of fuel bled through bleeder line 158 which is controlled by its end opening at 184.

The pressure in the chamber 154 behind the valve position control piston 150 is thus controlled by the amount of fuel that is bled from the opening 184 of the bleeder line 158. The opening 184 is controlled by the pivotal valve member 186 shown in the form of a rocker arm pivoted on a bracket 188'. A coil compression spring 190 urges the rocker arm toward closed position against the opening 184 and the action of this spring is resisted at the other end of the rocker arm 186 by a lever arm 192, which controls the position of the rocker arm and hence the opening 184 and the position of control piston 150 and the fuel ow valves.

The lever arm 192 is unique in construction and has a series of three fulcrum points 194, 196 and 198. These fulcrum points selectively rest on fulcrum wheels 200, 202 and 204. The fulcrum wheels are carried on the master fulcrum control rod 206 which is connected at its upper end to the valve stern 100 which was previously described. The lever 192 is thus pivoted about the fulcrum wheel which engages its fulcrum point to pivot the rocker arm 186 to determine in the amount of opening given to the opening 184 and thus determine the amount of fuel that will be bled to reduce the pressure of the chamber 154 behind the valve control piston 150. The fuel which escapes from the bleeder line opening 184 passes into the chamber 212 where it is fed back through a line 214 to the distributor line 12.

The flow valves can be normally controlled through a solenoid 185. The solenoid carries a valve 187 which, when the solenoid is energized, closes the bleeder line 158 to -permit the fuel pressure to build up behind the control piston 150 and move the piston to the right to close the valves No. 1, 2 and 3. The solenoid is controlled by an operators switch (not shown) connected to electrical leads 189 and used to shut olf the afterburner completely by closing the ow control valves.

The controlled position of the fuel ow valves is also fed into the control system. To feed back the valve position, the valve control piston carries a hollow cylindrical boss 208 in which is carried a coil compression spring 210. The outer surface of the cylindrical boss projects through a circular opening in the cylinder which contains the piston 150 and is sealed so that the fuel pressure within the piston will not escape.

The spring 210 within the hollow boss 208 carries at its outer end a plug 216 having a point 218 that engages the lever arm 192. Thus as the valves 1, 2 and 3 are moved to the left in the drawing they push to the left on the spring 210 which pushes outwardly on the plug 216 to move the lever arm to the left. This tends to pivot the rocker arm 186 in a counter-clockwise direction as illustrated in the drawing opening the opening 184 of the Vbleeder line further to reduce the pressure in the chamber 154. Thus only part ofthe control signal cornes from Air flow responsive mechanism In order to maintain the desired air tbfuel flow ratio tliej control mechanism must be varied as the air supply var-ies; The air supplied totheengine andE tothe; afteri burner'ise'ction may bemeasured by aI mechanism`- which is sensitive to the pressure differentialA or pressure rise throughithe compressor. Thus-,asA isl illustrated generally atf 25,y the pressure sensitive mechanism has a4 first line 302 Wliichi connects to the high: pressure side of theengine compressor and a second? line 304- which'. connects to the lowlpressure side. As will be appreciated by. those skilled in the art, alcompressorisV employed, as labeled in FIGURE; l, wherein the quantity of air delivered is a function of' pressure rise through the compressor; as will further be recognized, a flow measuring device may be employed' in the line` from the' compressor which measures flow in terms ofv pressure drop through the,l lin'e. Line 302' may be consideredto be connected to the high pressure side of the dow.v measuring device and line 304 to the'low pressure side.

The low pressure line- 304 leads* to the`r inside of bel'- lows" 306 and the high pressure' line.1 302 leads'l to the chambery outside ofthe bellowsas'enclosed by the casting 308;.` Within the bellows isa pressure compensating spr-ing: 310 withf a\ spring? tension regulator? 3122; Con`- nected to the bellows and movable therewith is a lever arlm operationf projection 314 which' engages a: notchiin the leverarm" a Thus, for example, as the bellows compresse indicating an increased flow' of air, the'lever. armiwill bei pivoted' in a' cloolvvisedirection'l asfis shown ii'r` the drawing to pivot the'- rocker arm 186': inA at counterclockwise directionl thus inoreasingl the' ovii` off fuel.l throughL the bleeder4 line 158 and movingzthe valve control piston? 1150i to' thel leftI to#` in+ crease* the openingiof the fuel controlvalves-1:, 2 and 3a Thisiwill increase' the" fuel" dow and automatically: maintain' the. propen fuel' tefair'ratio.'V A; re'du'ctioni in ilow of air will lia-'vet anl oppositefelfecntothat-previously described and will decrease the flow of fuel by closing the fuel: ow cortroll valves.

fer selecting' fuel'- zo'V air mit@ The fuel to air ratio maybe manually increased or decreasedby manipulating thefhand, lever 27 and this hand levert may be controlledto either'obtaini a desired fuel to air ratiofor, iff` the engine is usedn in aircraft, to obtain a selectedfightl Machnum'ber. The hand leverl 27- is-pivotallysupper-teer at its-'ba'se at 316: and carries a' cam 316 which', supports a; modulating; arm 3202 rlhisI modulating arm is connected at it'ebase: end to=a1pistonrod 322which reciprotsatesvinV response tor the' action of' the pressure ratio sensing; device 28- to' al'socontrolV the fueli toV ain ratio. Themodulating a'rmfhas a boss 324 atits" center carrying a pi`n-326f slidablyfl mounted in a slot'328in' alrrack-operatfing arm 330; The nackfoperatin g armis: pivotally' mount.; edto thefshellif; and is secu-redit@y a shaft'331 driving a segmentgean 332i which-:is in mesh witl a'raclc 334? carried ontthe': masten fulcro-mf controlL rod 206. Thus; as; isl illustratedg-` pivotali movement ofl the pinion 332 will be caused; by pivotalf movement of the arm 330 and will shift themasterrfulc'rum control rodV 206= upl or' down as is illustr'atedfin the drawing;

Pivotall movement of the arr'n 330;v as will= be recognized, can"` bef obtained by` moving' the manual arm 27 to pivot thefca'nn 318 thus raisingtthe modulating arm 320; The modulating arm; of course, can. alsso be'raised or' lowered by' the piston rod 322 which supplies the output of the pressure ratio' sensing device 28T.l Y

As: the master" tulerruin eontrolrod shifts axially, tper'- forms two functions; Fir's'tit moves the' fuel manifold sel"`etr pilot' valves 96l and '981 toeither stop or start the `flow* offfielihdividual-lyf througli therr distributor lines 14 O land 16, as will be determinedby the position of thepres sure regulator valves-64 andf74. The axial shiftingmovement of the master fulcrum control rod 206 also selects whichoftheafulcrumirollers- 200; 202=and7204wi11 act as a fulcrum forY the-lever mm1-922` In the position illustratedv in the drawings, thev roller 200 bears against the pointv 194 ofthe lever arm' 192andlthus the arm pivots about that: point. Thus; when the lever arm 192 is pivoted by the movement ofthe air ow sensor mechanism 251 operating by meansV of thelpii1-314 contacting one end of the lever arm;V a fairly extensive movement ofthe opposite end'of'thelever arm will be obtained; since the ratio ofi lengtl'r from thelowerend of the lever arm to the fulcrurn roller 200 to the length of lever arm from the fulcrum roller 200 to the-upper end is fairly large. A-s the master control fulcrumrodf 206'; however, is shiftedaxially downwardly, the fulcrum roller 200 will leave the point |194 yand the -fulcrum202 willmove on top ofthe point 196.` This changes the position of the effective fulcrum for the lever 1'92 and the response to the` lower end of the lever arm-will not be as` swiftas it was when the roller 200 wasv acting as the fulcrum; Neither will the movement of the lower end be as extensive.

When themaster fulcrum control rod 206 shifts even further downwardly, 4the' roller 204L will become the fulcrumandthusjthernount and speedof response of the lowerend oftlie leverarm'1922 will be greatly decreased foragiven movement off'tlie' upper end. Three fulcrums 200; 202 and204'arei cliosento'eindividually act' withl three raised1pointsf1^94g 196 and198--on the lever arm because there are three fluid flow contfr'olV valves in operation: Each time a liuid1 flow control` valve` istaken out of operation for closing a regulator-shutoff, valve 64. or 74, a differentpiv'o'tal'poilit for the f-l'crum must become effective. This will automatically smooth thev operation ofthe afterburne and the power output asl the number of combus'tion' Zones are reducedl Thus', as the master fulcrum control rod is shifted axially' downwardly, as shown in the drawing, the fulcrum 200`ceas`es t'o be effective and the fulcrum roller 202 takes over' atV the ex'aot pointv where the shutoff valve 74, which is positioned at the output of control valve No.l 3, is Closed. This', ae itwill. be recalled', is closed by the`-valve 98 openiii'glthevent line 90' to the drain line 60. Up to the pointv of.' the cl'osire of the shutoff valve 74, the amountvoffue'l'fed to the combustion area willr have been gradually reduced,v with the fluidA flow control valves 1, 2 and 3` moving toward. their closed position. When a different operatingv range or, in other words, a different fuel to air ratio is to be selected, one or more of the combustion Zones may be, out out by closingoff the distributor lines. Moving the master fulcrurn control rod 206 axiallylwill first shut orf the new in the line 16 and next shutoff the flow in the distributor line 14 by successively closing the valvesV 74 and 64. The moving of the m'ast'er fulcrum control rod will simultaneously shift the fulcrum. for the lever arm 192 from the roller 200 to the roller 202 tothe roller' 204, the latter roller constituting the fulcr'unr when only the fuel control valve No. 1 is operative.

The shiftingof these fulcrums performs two functions. First', the4 lands or the points 194, 196 and 198 on the fulcrurn` rod' are ofv different height. Therefore, as the fulcrum` is changed; from the roller 200 to the roller 202, the lever 1-92I is shiftedA bodily to the left to open the fuel flow controll valves in a definite step; This shifting compensatesl for the closing of the distributor line and maintains the valve area supplying the total combustion area the samev asA before the distributor line was shut olf. The same effect isrtrue' when the second line is shut olf by closing the valve' 641 The fulcrum moves to the roller 204EV movingV the fulcrum lever 192 bodily to the left to open valve No. I an additional amount to. maintain the ow of fuel to the combustion area substantially the same as before the valve 64 was closed. This creates a smooth transition of power when the number of burner zones is changed. The second effect of changing the fulcrum with axial movement of the master fulcrum control rod 206, is to change the ratio of the length of lever arm between the fulcrum and the controlled point and the fulcrum and the controlling point. Thus, when the fulcrum 200 is used, the ratio of movement between the lower end of the lever arm 192 and the upper end is fairly large but when the fulcrum 204 is used, the ratio is fairly small.

For example, if the diameters of the fuel valves Nos. 1, 2 and 3 are in the ratio of 6 is to 3 is to 1, it will be necessary for the valve stem supporting the fuel control valves to move with half the stroke control when valves No. 1 and No. 2 are in operation as it did when only valve No. 1 was in operation, if the rate of control change is to remain constant. If the transition is then made to valve No. 1 plus No. 2 plus No. 3, it will be necessary to have the valve stem move only one-third the stroke that it had when operating valves No. 1 and No. 2 together. Therefore, the lever arm ratios covered by the lands or points on the lever arm provides these proportional changes in the movement of the valve stem so that the total valve area open will remain the same as changes in the number of burner zones chosen to be in operation are made. In actual practice it will be necessary to supplement the simple linkage shown which is operated by the manual lever 27 with some kind of integrating device to avoid the hunting, off-on operation of the afterburner right at the selected flight Mach number or the selected fuel to air ratio.

Pressure ratio sensing device Although the mechanism shown at 28 does not form a part of the present invention, but merely contributes to aid in the determination of the selected fuel to air ratio from a further factor such as air density, a brief description will be useful. The mechanism shown generally at 38 has a static pressure tube 340 and a pilot pressure tube 342 which projects into a selected air stream. The pressure in the inner tube 342 is conducted into a sealed chamber 344 which houses a bellows 346. 'I'he bellows 346 is subjected to the force applied by the pressure differential ofthe air pressure 340 within the chamber and a vacuum within the bellows and movement of the bellows is transmitted to a valve stem 348 carrying cylindrical slide valves 350 and 352. The valve 350 when displaced axially downward, as shown in the drawing, opens the piston chamber 365 to the drain pressure line 360 and the piston chamber 362 to the fuel pressure line 358. The cylindrical valve 352 when displaced axially upward opens the piston chamber 362 to the fuel pressure line 358 and chamber 363 to the drain line 60. The piston 364 is connected to the piston rod 322 which is connected to the modulating arm 320 and thereby controls the fuel to air ratio through the control mechanism previously described.

The movement of the valve 350 must move the beam 372 which is connected to the valve stem 348. The beam is connected at the other end to the bellows 346 within the chamber 344.

The line of force of the valve stem 348 operated by the bellows 346 is at right angles to the beam 372, whereas the line of force of the rod 370 connected to the bellows 368 is at an angle. The effective resistance of the bellows 368, the expansion of which is controlled by the static air in the chamber 374, is proportional to the function of the angle that the rod 370 makes with the beam 372. This angle is controlled by the piston 364. The piston rod 322 is connected to an arm 376 secured to the pivotally movable frame 378 supporting the bellows 3'68.

Thus, the pressure differential between the static pressure and ram pressure within the tube 342 will determine the angular position of the support 378 for the a summary of operation will be helpful in appreciating the features of the invention.

Fuel enters through the line 18 to be pressurized by the air turbine fuel pump 20 and the fuel pressure supply line 24 distributes fuel to the manifold 26. Fuel is fed through fuel control valves 36, 38 and 40 to distributor lines 12, 14 and 16 which lead to combustion zones in the main afterburner combustion area.

The pressure drop across valve No. 1 is maintained constant by an air turbine pump control valve shown at 22. To accomplish this, a diaphragm 146 having lines 148 and 144 leading to the fuel pressure supply and the distributor line 12, respectively, controls the operation of the control valve 22. The control valve controls a gate valve 32 which supplies air through a chamber 34 to th air turbine 28. As the pressure differential across valve No. 1 is reduced, the diaphragm 146 moves to the left to move the valve stern 124 to the left and the valve heads 126 and 128 to the left. This bleeds air from the chamber 130 to the right of the piston and feeds air to the left of the piston to cause it to move to the right, moving the gate valve 32 to the right as shown in the drawing feeding more air to the turbine and increasing the turbine speed, thereby increasing the fuel pressure in the manifold 26.

The piston 114 is controlled by air which is fed to the line of the air turbine air supply 108. The air from line 120 enters a valve chamber 122 from whence it is fed up through either the lines 132 or 134 to either side of the piston, the other side of the piston being vented through the vent lines 136 or 138. Manually operated electrical control means functions in the same manner through the solenoid 164 which is controlled through electrical leads from a control panel by an operator.

The pressure drop across valves No. 2 and No. 3 is controlled by the separate pressure regulator valves 50 and 52. These valves maintain a constant pressure drop across the control valve and also function as shut-off valves to stop the flow through the distributor lines '14 and 16. By venting either of the vent lines 58 or 60, the pistons 54 or 78 in the pressure regulator valves will move the valves 64 and 74 against their seats to closed position. The venting of the lines 58 and 90 is controlled by cylindrical slide valves 96 and 98, the position of which is controlled by a master fulcrum control rod 206.

The position of the fuel regulating valves Nos. 1, 2 and 3 is controlled by signals fed in from the device 25 which is responsive to the flow of air through the compressor, by the manual control 27 by which the operator selects the fuel to air ratio or the desired ight Mach number, and by the pressure ratio sensing device which aids in the determination of the fuel to air ratio. The pressure ratio sensing device and the manual control lever feed in their signal by axially positioning the master fulcrum control rod 206. The axial position of this rod determines the number of combustion zones which will be in operation by operating the shut-off valves 64 and 74 in the distributor lines 14 and 16. The axial position of this master control rod 206 yalso determines which of the rollers 200, 202 and 204 will act as a fulcrum for the control lever arm 192. The pivotal position of the lever arm is controlled by the bellows 306 which compresses or expands in response to the amount of air flowing through the cornpressor which determines the volume of air that will ow into the combustion zone in the afterburner.

As the master fulcrum control rod 206 is shifted axially to change the fuel to air ratio, either the fulcrum roller to the eoniustion' area.

200 or 202i or 204'willengage the respective point 1594i or 19h or 1981o'n the lever arm-192?. Each ofv the fulcrum rollers willi successively change the operating length=ofi the lever arm so as to change the amount andi-ate' ofi response giveirtotherrocker arm 18dE which controls the"` opening 184'on'thebleederline152. The changeiin'flc'rum roller Will also laterally shift the positionof the lever arm to change thev positiof of the rocker arm` and change' the amount of fuel whiclris bledlfrom the bleeder line 156.

'Thisebleeder lin'e 1'56 controls thepressure in the chamber 154 iiir` back ofthe valve control pisto`n1150 and thus the position' oftherleve arm 192; controls: the position*` of the flow control valves. The position of the.Y valvesI is also fed to the ylever arm by means of the hollow boss 208, the spring 2-1'0l andi the plugy 2126, whichL bears'- ag'ainst the lever arm substantially at' its point of Contact with the valve controlling rocker arm 186.

Tlius itwill be seen that" I have provided animproved fuel control for an' afte'ibnrner whichk` meets the objectives liefe'inbefr'e set forth and which operatsto give anaccur'ate' regulation" andacontrol' of the flow of-'f'uel The numb'ef of ooinbustion Zesl'lsd in the afterbl Combustion areak may be cnanged at willl with' the change in fuer to oir ratio without affecting the performance of the-engine and a smooth transition is: obtained 4without 'sur-ges or fluctuations in power asthe fuel to air ratio is varied over a wide range.

The change in fuelr to air ratio automaticallycontrols the number of combustion zones in oper-ation and the number of fuel regulator valves in operation and the mechanism is operable from a single operating mechanism which combines the various control signals. The number of combustion zones can 4be selected with the use of a single pressurized fuel supply. Further, the pressure of `the incoming fuel and the pressure drop across the control valves are automatically controlled without affecting the performance of the machine or without necessitating a time delay or inconvenience utilizing the operating mechanism which selects the fuel to air ratio desired.

The mechanism is rugged and durable and will operate without the need of neadjustment and is well adapted to use in a turbo-jet type of engine.

I have, in the drawing and specification presented a detailed disclosure of the preferred embodiments of my invention, but it is to be understood that I do not intend to limit the invention to the specific form disclosed but intend to cover all modifications, changes and alternative constructions and methods falling Within the scope of the principles taught by my invention,

I claim as my invention:

1. A fuel flow control system comprising a pressurized source of fuel, a plurality of fuel ow control valves having their inlets connected in parallel to said fuel source, individual distributor lines connected to the outlets of the individual valves and leading to combustion zones, control means for said valves mechanically interconnecting the valves and moving them in unison to adjust the flow of fuel through each of the valves, individual shut-off valves in selected individual distributor lines, means` for individually operating the shut-olf valves to determine the number of distributor lines supplying fuel to the combustion zones, a lever connected to the llow control valve control means to control the position of the valves, condition-responsive means -connected to the lever to cause pivotal movement thereof to control the position of the ilow control valves in response to a change in condition, and `a movable fulcrum for the lever operative to change the amount and rate of response of the valves with the change in said condition, said movable fulcrum being operatively connected to the shut-off Valve operating means to thereby simultaneously change the ow control valve position in accordance with the number of distributor lines that are operative as determined by the position of said shut-off valves.

2. A fuel ow control system comprising a plurality I4 offuel' now' control valves arranged in parallel-ra's' to fuel flow being mechanically interconnected for movement; in` unison between an' open. andi a closed position, a pressurized" source of fuelconnected to the inlet side of the ow `control valves, individual distributor line'sc'oi1 nected to the outl'e't side of said flow control? valves, shut-olfl valvesi in certain of the distributor linesY adapted toI stop thev iovv` of fuel through saidlines, aA lever arm operatively connected to the -fuel ov'vV valves` to control theposition thereof, condition-responsive mean's connected to the lever ar-in to control the fio'v'v of' fel'- by regulating the position'of the leverf arrn and now control valves in` response to' a-condition change rela/ting" to fuel dw regulation', and Inain'control means operativelyconneoted to the shut-offV valves to' individually close the valves and connected; to tlielever arn and2 operative' to changel the effective lengthV4 ofl the'leve'r' arminaccordan'ce with the closing of the individual shut-oftj valves tov thereby ohange the positional response of" tlie ow control valvesv with respect to the condition-responsive means as the? number of? open' distributor lines changes.

3. A me'hanism for controlling the flow ofL fluid fuel comprising a plurality of flow control valves arranged in` parallel as to fluidflow' mechanically interconnected to move i'nu'nison', asource of fuel supply connected to the inlet? side of thev valves, aplurality of distributor lines connected to the outlet side of' the valves? and leading to@ a. combustion: zone; shut-oir valves certain of the distributor lines, a positional control for the .fuel control valves including a pivotal lever arm, the position of one portion of the lever arm controlling the position of the fuel control valves, means for delivering air to the combustion zone, means responsive to the quantity of air passing to the combustion zone and connected to the lever arm to control the position of `the valves in accordance with the amount of air fed to the combustion zone, and main control means individually operating the shutolf valves and connected to the lever arm to change its position with closing of the individual shut-olf valves to thereby change the position of the iiow control valves with the shutting olf of the individual shut-off valves.

4. A fuel now control system comprising a pressurized source of fuel, a plurality of fuel flow control valves arranged in parallel as to fuel ow having their inlet sides connected to the source of fuel, individual distributor lines leading between the individual valves and a cornbustion zone, shut-off valves in certain of the individual distributor lines and adapted to be operated individually to close off certain of the distributor lines, valve position control means operatively connected to the fuel flow control valves and including a pivotal operating lever means for delivering a now of air to the combustion zone, means responsive to the amount of air flowing into the combus-A tion zone and connected to said operating lever to control the position of the fuel valves in accordance with the air ilow, raised fulcrum points on the lever adapted to supply movable pivotal points for the operation of the lever, said fulcrum points being of different elevations to change the position of the -fuel flow valves and being in different locations to change the amount and rate of response of the fuel ow valves as controlled by the air ow responsive means, and a movable support adapted to individually contact said fulcrum points to vary the position and pivotal point of the lever, and a main control means connected to said movable support and connected to said shut-off valves to change the pivotal position of the lever with change in the number of distributor lines that are closed.

5. A fuel ow control system comprising a pressurized fuel inlet line, a plurality of fuel valves communicating on their inlet side with said fuel line inlet and arranged in parallel as to fuel ow, a plurality of separate fuel supply lines for leading to a fuel burner and connected to the outlet side of said fuel valves, separate shut-off valves located in at least some of the fuel supply lines and being individually controllable to close the valves to stop the ilowof fuel in the individual lines, first means for separately closing the shut-off valves, and second means controlling the position of the fuel valves, said first and second means interconnected for substantially simultaneous operation with said second means increasing the opening of said fuel valves in the lines having shutolf valves remaining open as the individual shut-olf valves are closed to compensate for the reduction in number of lines supplying fuel so that a uniform rate of change of fuel ow is maintained.

6. A system for regulating the ow of fuel comprising a plurality of ow control valves, a pressurized fuel line communicating with the inlet side of said flow control valves, a plurality of separate outlet lines for leading to combustion zones from individual control valves, sepa. rate shut-olf Valves in a number of said outlet lines to individually control the ow in said lines, rst means operatively connected to the shut-olf valves to selectively open said valves, and second means connected to control the opening of said flow control valves, said rst and second means interconnected to cause said second means simultaneously to decrease the total opening of the flow control valves in lines having open shut-off valves as one of the shut-off valves is opened so that a smooth rate of change of ow of fuel will be obtained.

7. A fuel control mechanism for supplying fuel to a combustion area comprising a pressurized source of fuel, a plurality of rigidly interconnected individual fuel ow control first valves arranged in parallel as to fuel ow and connected to said pressurized source of fuel, individual distributor lines leading from the discharge side of said individual fuel ow valves to a combustion zone, means for controlling the position of said fuel ow valves, individual shut-off and pressure regulating second valves in the distributor lines, means for individually closing said second valves to shut-off individual distributor lines, and means responsive to pressure differential across individual rst valves connected to operate said closing means for said second valves.

References Cited in the le of this patent UNITED STATES PATENTS 2,127,172 Hermitte Aug. 16, 1938 2,503,048 Iield Apr. 4, 1950 2,644,513 Mock July 7, 1953 '2,668,415 Lawrence Feb. 9, 1954 2,739,442, Neal et al. Mar. 27, 1956 2,750,741 Leeper June 19, 1956 2,871,659 Chamberlin Feb. 3, 1959 FOREIGN PATENTS 526,869 Germany June 11, 1931 731,524 Great Britain .Tune 8, 1955 (Corresponding U.S 2,871,659 Feb. 3, 1959) 

